Many electronic devices, such as sensors, are designed to operate in harsh environmental conditions. In many cases, these electronic devices are used to provide information, guidance and feedback that is critically important to its operator. Such devices are often subjected to harsh environments such as elevated temperatures, sub-freezing temperatures, thermal shock, and/or corrosive atmospheres. In addition, these devices may also be subjected to excessive mechanical stresses, such as mechanical shock and vibration.
Among these electronic devices are the instruments and tools typically used in oil and gas drilling operations. One such device, referred to as a “measurement while drilling” (MWD) instrument, is used in oil and gas exploration. These MWD devices are often positioned within the structure of the drill and are used to help an operator guide the drill to regions of oil and gas deep within the earth. These devices generally provide information regarding temperature, depth, position, and pressure at and around the drill head. As such, these devices are often subjected to temperatures in excess of 150° C. and, as the drill bores through the earth, mechanical vibrations in excess of 0.50 G2/Hz power spectral density (PSD).
Electrochemical cells or modular battery packs are often used to electrically power these devices. In many cases, electrochemical cells or modular battery packs are positioned within the device. Therefore, these electrochemical cells and modular battery packs are also often subjected to the same environmental conditions, that is, the thermal and mechanical stresses, as the devices they power. Hence, these electrochemical cells are typically designed to withstand these harsh conditions.
One of the important design considerations of a modular battery pack is the interconnect that electrically connects two adjacently positioned electrochemical cells together therewithin. The interconnect is a critical component that provides a conduit for electrical energy to pass therethrough. In general, the interconnect is positioned external to the electrochemical cell or even a modular battery pack when electrically connecting two or more packs together. Therefore, the interconnect has an increased exposure to thermal and mechanical stresses that makes it prone to possible breakage or becoming disconnected from the electrochemical cell. If the interconnect were to become damaged or disconnected, electrical power to the device being powered could be compromised. This, therefore, could be particularly problematic if the device is in a remote location and/or at a significant distance away from the operator.
Typical modular battery packs of the prior art have relied on a metallic tab, generally made of nickel or stainless steel, to electrically connect adjacent electrochemical cells. The prior art tabs generally comprise multiple folds in which the tab is folded over itself in an “accordion-like” fashion. These folds are intended to provide some mechanical resilience as the adjacent cells are spaced apart from each other. However, finite element analysis (FEA) modeling has indicated that under extreme mechanical vibration and temperature conditions, these prior art tabs may be susceptible to breakage. For example, under computer modeling conditions of 20 root mean square acceleration (Grms) random vibration from 5 to 500 Hz at temperatures ranging from 75° C. to 210° C. for four hours, the prior art tabs are prone to shear and break along the folds.
Therefore, there exists a need to provide an interconnect with a robust design that is capable of withstanding the increased thermal and mechanical stresses associated with powering devices in harsh environments, particularly MWD devices. The present invention fulfills this need by providing various embodiments of an electrochemical cell interconnect assembly that is designed to withstand temperatures in excess of 150° C. and mechanical vibration greater than 0.50 G2/Hz PSD.